docs: def parse_timedelta(deltastr):
      """
      Parse a string describing a period of time.
      """
      matches = TIMEDELTA_REGEX.match(deltastr)
      if not matches:
          return None
      components = {}
      for name, value in matches.groupdict().items():
          if value:
              components[name] = int(value)
      for period, hours in (('days', 24), ('years', 8766)):
          if period in components:
              components['hours'] = components.get('hours', 0) + \
                                    components[period] * hours
              del components[period]
      return int(timedelta(**components).total_seconds())